A rolling-mill stand which makes a rolled product, particularly rolled strip, can comprise a pair of working rolls, which if necessary are braced by a pair of supporting rolls or by a pair of supporting rolls and a pair of intermediate rolls.
In this rolling-mill stand the working rolls and/or supporting rolls and/or intermediate rolls can be axially shiftable relative to one another and each roll of at least one of these pairs of rolls is provided with a curved contour extending to the roll body ends.
These curved contours are provided for both rolls of that roll pair, over a portion of the rolled product width. The curved contour extends over the entire roll body length of each roll and both roll bodies have a shape in which both roll body contours entirely complement each other in a certain relative axial position.
A rolling-mill stand of this type is described in European Patent 0 049 798. The roll gap shape is influenced by the features disclosed therein. A special position for the rolls in regard to the rolled product edges is not disclosed.
The working rolls are braced as usual over their length on intermediate or supporting rolls so that the roll force or load exerted by the supporting rolls is transferred over the entire length of the roll body. This has the result that the ends of the working rolls protruding laterally over the rolled product and thus not participating in the rolling process are bent by the roll forces exerted on them in the direction of the rolled product.
Furthermore in roll stands with stiff working rolls this damaging bending of the working rolls during rolling of a centrally rolled section or product causes a weakened rolling of the center portion of the rolled product and an excessively strong rolling of the edges of the rolled product. This effect is particularly noticeable in operation with varying rolling conditions such as sheet or strip temperature and varying roll forces as well as on rolling of different width products.
To eliminate this disadvantageous effect as set forth in German Patent 22 06 912 in six-high rolling-mill stands, the intermediate rolls are adjustable to fit the rolled product width so that one end of the effective roll body of the upper intermediate roll is placed in the vicinity of one rolled product edge while the opposing end of the effective roll body of the lower intermediate roll is placed in the vicinity of the other rolled product edge. Thus each working roll contains an end portion free from pressure due to the associated intermediate roll.
Furthermore in these rolling-mill stands, roll bending devices engage on the ends of the working rolls. The rolls are provided in the conventional way as symmetrically shaped and roll bending devices are provided. An end portion of the intermediate rolls is tapered conically in a comparatively short region with the disadvantage of a stepped change of the load distribution in the vicinity of the change in the angle of taper.
A more serious disadvantage of this known roll arrangement is that the effect of conical tapering and the axial adjustment of the intermediate rolls is limited except on the roll strip edges and the center region of the strip can in no way be influenced by it.
In German Patent 22 60 256 a roll stand with devices for axially shifting the working rolls in opposite directions on changing the rolled product width is disclosed so that one end of the working surfaces of a working roll is held between a rolled product edge and the end of the associated supporting roll.
Moreover intermediate rolls are also provided so that the upper intermediate roll is shiftable in the same direction as the lower working roll and the lower intermediate roll is shiftable in the same direction as the upper working roll. Also a conical tapering of only the ends of the intermediate rolls is provided with the above described disadvantageous effects.